204 



NEW YORK STATE MUSEUM 



Schizophoria ? amii nov. 



Plate 44, figures 21-25 



Shell of medium size, transversely subelliptical in outline. Ventral 

 valve with slightly prominent beak which is not depressed but from the 

 umbonal region departs a low median sinus which widens posteriorly and 

 covers one third the width of the valve at the anterior margin. The dorsal 

 valve is the more convex specially in the median region which is elevated 

 into a broad ridge corresponding to the concavity of the ventral. From this 

 central ridge the sides slope somewhat abruptly and with a slight depression 

 postlaterally. The surface is marked by fine angular radii very like those 

 of Dalmanella lucia and are rapidly increased by implantation. 

 Sometimes these striae are seen to end abruptly in elongate punctae as in 

 some species of Rhipidomella (R. penelope Hall, Hamilton). The 

 surface is crossed by fine and obscure concentric lines. On the interior the 

 ventral valve bears flabellate muscle scars but it is not known whether 

 the scars of the dorsal valve conform to those of Schizophoria. Specimens 

 of this species are easily confounded with those of Dal lucia but the 

 contour of the two is exactly reversed. 



Dimensions. A normal specimen measures 18 mm in length and 20 

 mm in width. 



Locality. Rare at Grande Greve. 



Specific name. H. M. Ami, eminent Canadian paleontologist. 



Dalmanella lucia (Billings) 



Plate 44, figures 8-20 



Ortliis lucia Billings, Palaeozoic Fossils. 1874. v. i, pt 2, p. 35, pi. 3, fig. 4, 4a 

 The original description of this species is as follows : 



Shell subcircular; outline concave on each side of the beak; cardinal angles broadly 

 rounded; sides gently convex; front either broadly rounded or with sometimes a portion 

 in the middle projecting. Ventral valve moderately convex, most prominent about the 

 middle or a little above; cardinal margin and sides slightly compressed; umbo well 

 developed, carinating the valve in the upper half; beak minute, incurved at a right angle 

 over that of the dorsal valve, and apparently in contact with the same; area very small, 

 scarcely visible. Dorsal valve very slightly convex; a barely perceptible mesial depression 

 originating in a point at the beak and gradually widening to the front, where it flattens 

 about one half the whole width of the valve. Beak minute, but distinctly visible when 

 that of the opposite valve is removed; cardinal edge slightly sloping on each side of the 

 beak; area not visible. 



Surface with fine subangular striae which bifurcate several times; those at the car- 

 dinal angles, and for some distance below, curving upwards as they approach the margin; 

 four or five striae in the width of one line. 



Width of the largest specimens seen, eleven lines; length, about nine lines. 



